Automatic telephone-exchange system and apparatus.



AUTOMATIC TELEPHONE EXCHANGE SYSTEM APPARATUS.

APPLICATION I'ILIID FEB.12, 1904.

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NO MODEL- Iig. 2 7i l(,/ u u PVITNESSES: loo I Mum M By Max m ,J/ I v ATTORNEY.

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TATENTED 001:. 11, 1904. A. B'ULLABD & L. A. PALK.

AUTOMATIC 'TELEPHONE'EXGHANGE SYSTEM AND APPARATUS.

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' WITNESSES.

ATTORNEY.

UNITED STATES Patented October 11, 1964.513"

PATENT OFFICE.

ALBERT M. BULLARD, OFNEVV YORK, Y., AND Louis A. rank, or BOSTON, MASSACHUSETTS. ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COlWIPANY, A

CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM AND APPARATUS.

SPECIFICATION forming part of Letters Patent Iva 772,024, dated October 11, 1904.

Application filed February 12, 1904. Serial No. 193,296- (No model.) I

To (l/Z] whom it inlay concern:

Be it known-that we, ALBERT M. BULLAaD, residing at New York, in the county of New York and State of New York, and LOUIS A. FALK, residing at Boston, in the county of Suffolk-and State of Massachusetts, have inventied certain Improvements in 'Automatic Telephone-Exchange Systems and Apparatus, of which the following is a specification.

'The invention about to be described is an improvement in automatic telephone-exchange apparatus andcircuits, havingparticular referencetosuch exchanges as are limited to a small numberof subscribers circuits, some or all of which may be. party-lines or lines having a plurality of subscribers connected thereto, and is Well adaptedfo'r use in small towns,

' oflics, or Warehouses and for like conditions of installation where an inexpensive type of apparatus is desirable.

The automatic exchange apparatus as described herein is designed for ten metallic telephone circuits extending from their re 'spective substations to the central station,

where is located a common source of electromotive force supplying current for 'operating the system and for signaling, the telephonic transmission being eflected by batteries at each substation. On the assumption "that? many of the small places where an exchange of this character would be installed will not be equipped with facilities for charging secondary batteries the system is arranged to be .operated by primary cells, whichare comparatively easy of control. At the substations'the apparatus consists of the'usual high-resistance call-bell and condenser in a bridge or inductively continuous connection'between the line conductors, with telephones, a selectingkey and a ringing-key respectively adapted to ground the respective line conductors alternately in a normally open branch parallel with the bell'and condehsen- At the central station :each conductor of each telephone-circuit is connected to a polarized line-relay, one of which relays is ter'med the selecting-relay and the other the ringing-relay. Both relays are in'circuit with the central battery first, the selecting-magnet which is operated 4 only when the selecting-relay'is inert and the ringing relay is excited, thus economizing the current-supply, and, second, the retain-' ing-pawl magnet adapted to attraet its armature as long as either of the line-relays is excited. The selector-inagnet is adapted. to rotate selector-springs step by step against the tension of a recovery-spring round a )dial on which are mounted two innersegmental conductor-plates which form the terminals of the line conductors of the circuit and a series of studs contiguous to and outside of the said plates and each representing the terminal of a line conductor of an associated substationcircuit, and each pair of selector-springs acts as a movable connector to join any stud with selector-springs of each substation-circuit- 7 switching device at the central station normally rest upon two studs, forming the terminals of an interruption in each line conductor and to unite the same; but when the *selecting-key is operated to connect with another circuit the conductors are opened at these points and connection made by the selecto-r'.springs with the semicircular plates and studs of the line wanted. The movable selector-springs are thus utilized for the double purpose of' selecting and switching, et' fecting great economy'in the number of parts comprising the selector device. selector has been operated thesignal-key is pressed a number of times corresponding, ac-

cording to the code, to the wanted substation,

and a pulsating ringing-current of single direction is sentover a grounded circuit in- LII cludingthe conductors and hell o l the calledsprings of the selector are automatically re turned to their normal contacts by the said recovery-spring.

The invention also relates to combinations of circuits and apparatus more fully and specifically described hereinafter.

' Reference is made to. the accompanying drawings, in which-- Figure 1 is a front view of the substation telephone set.' Figs. 2, 3, 4, andfi are respectively an end elevation, side elevation, a top view, and a-bottoln view, of a selective and switching deviceused atthe central station; and Fig. 6 is'a diagram illustrative of the substation apparatus, circuits, and linewires of two subscribers only, with the circuits and equipment of the exchange, the terminal connections of the remaining substation-circuits being simply indicated at the exchange apparatus.

In the drawings, X and Y represent the substation-terminals of the telephone-circuits 'Lf and L, whose conductors 2 and 3 and 2 and 3" terminate in automatic selective and switching apparatus H and H 'at the central station Z. 'The circuit L may be called No. 3 and The apparatus at the substations consists of a high resistance polarized call-bell B, biased or adjusted to respond to a pulsatory'or intermittent current of single direction, and a condenser c in a bridge 4 between the m ain conductors 2 and 3, together with the station telephones and the selecting and ringing; keys K and K in a normally open branchof said bridge extending between the points 5 and 6 thereof. The wire 00, including the telephonereceiver t, connects; the point 5 to the secondary winding i of the induction-coil I, the

'and 13, having anvil-contacts l5 and 12, supported on springs 14 and 11, and normally closed separable contacts at 17 andf16 in series with each other. When manipulated, the phone being off its hook-switch, the selecting key K closes itsvworking contact 15, thus grounding the main conductor 2 and severs its normal contact 17, thus opening'thernain circuit toward main conductor 3, while the ringing-key K closes centact 12 and opens.

contact 16, thus grounding main conductor 3 and opening the circuit toward main conductor 2.

I When the receiver is taken from the switch s, a conductive circuit is closed through the substation between conductors 2 and 3 by way of the bridge-conductor point 5, conductorm,

switch-contact stop 8, the switch .9, wire 10, closed contact 16, springs 11 and 14, closed contact 17, and wire 18 to point 6. The circuit L is assumed to have more than one substation associated withjit, and the bridge? between the conductors 2 and'3 conventionally represents a second station X Figs. 2, 3. 4:, and 5 refer to the selective and switching mechanism located at the central office end ofeach substation-circuit, which will now be described. The said mechanism has a metal base-plate 100,- upon which are secured the electromagnets M and-1V1, the former-constitutingthe selecting-magnet and the latterthe ringing-magnet. Two standards 101 .and 102 extend outward from the plate 100 beyond the poles of the magnetspools and their outer ends are provided with holes to receive the ends of the rods 103 and 104, upon the outer ends of i which are pivoted the armatures o and j. The armatu-res extend across the poles of the magnets and on .one end have downward projections 105 and 106, respectively, and in the drawings the vsaid armatures are shown attracted. 94 is a double back-stop provided with the stops 86 and 88, secured to standard 102 by screw and pin 107 ends and 85 are retracting springs .Inade V-shaped, with a; central coil adapted torest upon the endsof the rods 104 and 103, the ends of their outer legs bearing upon the'pins'8 9 and ofthe projections 106 and 105, while their inner" legs bear upon the pin 10?. Upon the end of the projection 106 is a pawl wt to engage with the teeth'of the ratchetwheel-.V upon the spindle k, which is supported at each end by the standards 101. and

102 the said spindle being provided with a' recovery-spring S, secured thereto at one end by the screw 108 and at the opposite end having its end entered in a'hole 109 in the standard 101. .The pawl nis, pivoted on the-screw .92 and is provided with" a'stop-pin'90, and at the end of projection is a'retaining-pawl j limited by the stop-pin 93 and adapted to engage the teeth of the .wheeland prevent its back-wardmovement. Upon the upper side of the standard 101 is a stationary disk or dial g, of insulating material, into which-near'the edge are inserted a series of metal buttons r,

twenty-two in number, and inside of the buttons are two semicircular or segmental plates, of metal, :2 m, between the endsof which are buttons 1* and 1". The. buttons are connected with binding screws it upon the under side of the disk.. The spindle k extends through the disk g and'bears uponits end a hub '20, upon which is an insulatingning, the ends of the two metal fingers (1 another non-conducting nect the buttons 1* r and r r, and when in motion they rotate about the disk in a clock- -wise direction.

' Fig. 1 is a representation of the external appearance of the substation apparatus, the operative parts being inclosed in the upper part 115 and the batteries in the lower part 116, the selecting and signaling keys K K sea 3 by these relays reference may first be made to the local circuit including the retainingpawl magnet M which is'closed by both relays as follows:. The armature e of relay R closes this circuit at the auxiliary stop 32 over a path beginning at the positive terminal of the cen- 39,(insulated from the 'arinature) contact-stop 32, 'conductors 33 and 3,5, retaining-pawl magnet hl conductor-s39 and 27 to the negative pole of the battery. The relay R closes the same circuit at c'onta'ct -15 over a path from the said positive terminal of battery E E through condu'cto'rs 27,43, and 14, contactstop 45, armature g, conductor 35, magnet M and conductors 39 and-27 back to the battery. It is seen that this circuitwhen closed by the armature of either relay in its forward posithe cali-bell B, and telephones? I? being appro- -tion will keep the retainingpawl pressed priately indicated.

As represented in 6, the L circuit No. 3 and the L circuit No. 9 are in their condition of disuse and the selecting and switching springs d and (Z are upon their normal buttons .in a position to be called by each other, the

said normal buttons of circuit L being connected to the conductors 2 and 3 as follows:' from conductor 2 by conductor 2 to button r fingers '(Z, button 7*, from which the line No. 3 is extended to the selecting and switching mechanism of line No. 9 and to multiple 7 buttons at the mechanism of all other lines of the system, by conductor 7 8, a branch 23, from conductor 24 connecting to button 3 at the apparatus H, and from conductor 3 by conductor 41 to button. 9*, fingers (Z button W,

and conductors 53 and 56 to button 3 otthe apparatus H The conductors 2 and 3 have a connection by means of the conductors 59 and 51 with the line-relays R and R, respectively, and through the bridge 27, which includesbattery-sections E and E provided be tween them with a branch 27 to ground. R is the selecting-relay, and R the ringingrelay, both being polarized to assist in the ringing operations.

The details of the circuits will be referred to in the description of the operation as follows:-

It maybe-assumed that a call has originated with substation of circuit L, (No. 8,) who wishes to connect with substation Y of circuit L (No. 9.) The receiving-telephone t is removed from the switch a, which rises and en gages the stops 8 and 9, thus completing a circuit from the switch through secondary coil 2' bridge conductor 4:, conductors 2' and Y59, relay R conductor 27, battery E E conductor 51, relay R, oonduct'or 3, bridge conductor i branch conductor 18, and through the keys K and K back to the switch. The selecting-relay R and ringing-relay R are energized, the armatures g 71 of relay B being attracted to'th'eir frontfstops 45 and 4:9 and the armatures e f of relay Rito their forward stops 28 and 26. Of the several circuits controlled against the ratchet-Wheel V and that opening and closing the metallic circuit of line L, formed through the line conductors 2 and 3, results merely in the backwardandforward movement of the retaining-pawl J wh ich does not move the ratchet-wheel. To select line No. 9, which we have assumed is circuit L the attendant at X presses the selecting-key K nine times. This may be done at any reasonable rate of speed, and in response to each pressure the selector-spindle 7:: is rotated one step in the following manner? The key -is pressed hard against the stop 15,- bending the spring 14. away from the normal contact-stop 17 grounding themain conductor 2 and opening the main, conductor 3 side of the line, and relay R therefore remains energized, being maintained ina grounded circuit from earth branch 27* to the substatiomground, including battery E, conductors27 and 59, relay R conductors 2, lg-and w, switch .9, wires 10 and 11, stop 15, key K, and wire 19-, while the relay R is deenergized so that its armature 'ghfalls through the selecting-magnet ,M,-w-hich, beginning at the positive side of the battery E E continues through conductors 27 and 4:3, stop 32, conductor 33, armatureg, stop 46, conductor 38, magnet M, and conductors 39 and 27 to battery. This energizes the selecs tor-magnet M and causes its pawl 92. to revolve the selector-fingersfrom the buttons 1* and 1* r to the buttons 1', which'are the terminals of line No. 1, and bring them into contact with the semicircular universal terminal plates (1: and 0. When the key K is released, the magnet M releases its armature, which falls back the key is again pressed, and nine successive depressions of said key will thus advance the selector-fingers to the buttonslQ 9 of line No. 9. The double springs (Z, one at each ,end of the seiectorarm, make constant frictional-contact with the successive line-buttons and are held in their advanced position by the retaining-pawl magnet M which receives current back upon stop 46 and closes a localcircuit tral battery E'E conducto rs 27 and 43, spring ready't'or another step, which takes place when I 7 through the stop 32 of relay R as already described. I Having stepped the selecting and switching springs tpthe buttons 9 9 of the ap paratus H, a.circuit is established with-the apparatus H". associatedwith the circuit No. 9,

and the sebscriberatgi now presses the ringlug-key K once if thesiibsoriber'at'Y is the only station on thefliireiiit L If, however,

'thcreare more stations on the circuit, the key is pressed anumber of times, corresponding to the cqdernumberof the station, and at each pressure of the .key the conductor 2 is opened and the relay Rdenergiz edallowing the armature e to be retracted against contact-stop v 1 29, andthus ground the ringingcircuit at one end,thecircuit through conductor 3 and the excitement ofrelay B being maintained to hold the retaining-pawl in position. The circuit for the ringing-current may be traced from source of current E the rhythmical vibrator 7 0, conductors 62 and 60, armature h ofrelayR,'stop 49, conductor 40, stop 48 and ar- .mature f of relay R", conductor 14, segmental plate at, selectozgspringgi, .button 9, conductor 57 tolbuttonr of apparatus Hflselector-spring d, button r, conductor 24,line.conduotor 2,

call-bel'l B, and condenser c of station Y, mainline conductor 3, conductor 41-, conductor 53, to. "button. 9 0f apparatus" H, 'spring'd plate z", conductor 21', armature e of relay R stop,

29,,imd branch to ground, The condensers c and-6"- are'i'iormally-short-circuited by the selector-spring d"-of each selecting device H HTesting upon the buttons 1" 1- and ductor 4 1, (or 41,)- sothat upon the receipt of a call the called line is in condition to be sig naled most effectively and to be combined with the calling-line insuch that the bells would not be rungloud enough.

Another 'reasonfor keeping the condenser o short circuited when, line L? is called is to avoid having. twoc'ondensers on one side of the combined lines, and but one condenser on the other. In allof these opra'tionsthe receive'r't remainsofifrom the switch, and the circuit when the keys are not being manipulated is throughth'e polarized liBe-relaysR R and battery E-E fJonsequently therelayarmature's', are attracted, and armature g ofrelay R presses the spring 22 against the stop, 47, thus closing the circuit of the source of puleating current E via conductors 68,64, and

6.6, stop 47, spring 22, conductors and 63, vibrator-rna'gnet W, spring 76, stop 77,sp-ring 1'- 5,

and cpnductei' 74, and setting the rhythmical I tween the two battery-sections E E COIl- I of the ringing-relay R the ground-stop and a contact-stop branched Inagnet W it makes, contact alternately with from the positive pole, and so sends apulsating ringing-current of single direction over the circuit L bythe path previously traced through the armature la of relay R and the armature f of relay R During the ringing operation the relay B, of the called line is shunted by the temporary ground Gr at the back-stop 29 of relay R and ringing-current is diverted 'round relay R directly to said ground. This arrangement, however, involves the inclusion of the said relay R. in an incidental local circuit between the said tern porary ground and the ground attached be- This circuit is traceable from the former ground by stop 29, armature e of relay R conductor 21,-switchplate 00 brush-spring d, button 9, conductor 53", brush-spring d of mechanism H conductor 41 to the magnet-coils of relay R", conductor 27, battery-section E and conductor 27; but the temporary connection of the relay R. in this circuit is of no consequence, since though it brings about the excitement of said relay and the attraction of its armatures once for each stroke of the ringing-key this is not followed by any Bperation of the selecting-magnet M for the reason that the circuit of said magnet remains open between" the points 32 and'39 During ringing the relay R of the circuit L retains its armaturesjin their forward position,so that by means of the already-traced local circuit passing through the armature g and contactstop 45 the retaining-pawl 7' remains in en- 7 gagement with the ratchet-wheel V and prevents the sele'ctor --spindle from recovery. When the subscriber Y answers the call by lifting his receiver from his switch, his relays R andR steadily attract their armatures; but these movements are without significance anddonot cause the selector H to advance, for armature g of relay R leaves the stop 46 before the armature e of relay R makes contact between the spring 39 and stop 32,, and therefore the selecting-magnet M is 1 not energized. Telephonic transmission may now be efi'ected over the following circuit: secondary winding 2' of inductioncoil'at station X, receiver 25, conductors 4 and 2, c'ondenserb stop 26, armature f, eonductor 14, segmental plate in, switching-spring d, and button' 9, conductor 57, button 1*,

switching-spring d, and button 0? of switch mechanism. H conductors 24 and 2, bridge a", the telephones and keys connected therein at station Y, conductor 3, conductor 41", button 1' switching-spring 0Z button 7', contoo ductor 53, button 9, switching-spring d, and

semicircular plate m of switch mechanism H, conductor 21, armature 6, stop 28, conductors 31, 56, and 50, condenser 0 conductor 3, and

who refuses to hang up his telephone, and

therefore- 2. subscriber can at willfree himself from any other line under all conditions.

It will be seen that the selecting mechanism of a call-originatingline at the first.ro tary step of the selector-spindle disconnects its selecting and switching apparatus from:

the multiple conductor'78, this remaining disconnected until the spindle returns to zero, so that the process of selecting and ringing cannot be interfered with by other subscribers calling such line and disturbing its relayswith ground shunts ;,and ringing current.

"Upon the termination of conversation the rerlceivers are returned to the suspension- 'switches's, which are thereby depressed and tion with the line of--Y, because the said switching-springs d d of the switch Hiwould 5 have been moved from the local switch-butopen the line-circuit, and the line-relays being dem'agnetized the retaining-pawl falls back and the recovery-spring S returns the switching-springs to their resting positions.

Should the line of the called subscriber Y have been already. called by another station and connected therewith before its selection by subscriber X, the'latter would be made aware of that fact by hearing conversation, for in this case the switching-springs (Z d of theapparatus H of "line L have not been moved from their normal position, and connections will therefore be established between the main conductors of lines X and Y, as previously stated in describing the selection of subscriber Y by subscriber X, when the line ofthe former is at liberty; but if the subscriber Y in the previously-made connection referred to had been the selecting party then X in selecting would fail to establish connectons, the intermediate circuit connections belng thus opened. Thus 1n the former caseof the busy-condition of the wanted line the calling line may after selection hear converand ringing keys are manipulated in exactly the same way as in calling another line, and if X is No. l on his line and X is No. 2 the selecting-key is pressed three times and the ringing-key pressed tW ice.' The first act steps his selector-springs cl (F into contact with the 'buttons 3 3 and 'the segmentalplates 11: 1: of

their own line No. 3. One of said buttons is connected by Wire 23 with the conductor 24: and lineconductor 2 in order that ringingcurrent may be sent over said lin'econductor 2 notwithstanding that the multiple conductor 78 has been opened at buttons 1* 1' ,by'the selective act. The other button, 3, might be dispensed with, for it plays no part either inrlnging or transmission, but is needed as a' mechanical support for one selector-spring. In signaling the substation X at each depression of the kcyK the relay R releases its armatures and the current traverses the following circuit: from the grounded source of ringingcurrent 13 by vi'brater -70, conductors 62 and 60, armature-h of relay R, stop 49, conductor 40, stop 48 of relay R armature f, Wire 14, plate m switching-spring (Z, button 3, \conductors 23, 24, 2 and P, bell B, and condenser a, point 6, conductor 18, and through key K to key K and ground at station Xi. the bells bridged on the line are rung, including that of subscriber X. A negligible amount of the ringing-current returns to the central station over the conductor 3, through the relay R and battery E to ground without, however, disturbing said relay,-as the pulsating ringing-current is of the samesign as the battery-cement flowing therethrough. A small.

amount of ringing-current also'flows to ground All 0t" from the junction-point 59, through the relay R and battery E, but without operating said relay, which is polarized to be irresponsive to positive current entering its winding from the side toward said junction-point. It is essential that the ringing-current shall not affeet the operation of ringing-relay R that .its armature f shall rest firmly upon the backstop 4L8 when the ringing-key is pressed, and shall move promptly into the forward position upon" stop 26 when'the' key is released,

and as the relay R must remain in the current-supply circuit with one terminal connected to line and since itis necessary to apply ringing-current to the same side of the line at virtually the same point as-that of said relay connection a pulsating ringingcurrent is used instead of the ordinary alternating cur,-

rent, the relays R and R being polarized IYIO ' successively, and a retainingelectromagnet,

device having a rotatable switching-connector, and terminals in the path thereof of branch conductors of the main line and also termi nals of conductors to theswitchi-ng'devices'of all the other'members of the group, a selecting-electromagnet [to rotate the said switching-connector into contact with said terminals to hold the said connector in position on the terminals of the circuits; the said apparatus adapted to become operative uponthe closure of' said bridgeby the automatic switch causing said relays to close independent local circuits through-the retainingmagnet, and upon the subsequent manipulation of the selectingkey to deenergize the selecting polarized linerelay opening one of said independent localcircuits and closing another local circuit through said selecting-magnet, substantially as set forth. I

2. Inan automatic telephone-exchange, the

combination of a'group of metallic substationcircuits, apparatus at each substation of said metallic circuits consisting of a call-bell and a condenser in a bridge betweenthe line conductors, with telephones, a selecting-key and A a ringing-key in parallel with said bridge, the

selecting-key being adapted to gr und one line conductor and theringing-key to ground the other line conductor; apparatus at the central station consisting of a polarized relay in each line conductor said relays having their helices connected to the opposite poles of a centrally-grounded source of current, and a selecting and switching device operated through said line-relays having terminals of its own main-line conductors and terminals of the main-line conductors of the other circuits with which itis multiplied, and a rotatable switching-connector adapted totrail over said terminals, a selecting-electromagnet adapted to rotate the switching-connector upon the man'ipulation of the selecting-key, and a retaining-magnet to hold the connector in position upon the line-terminals, successively operated upon the closure of the main-line circuit by the automatic switch through the medium of one or both of the line-relays, as set forth.

3. In an automatic telephone-exchange, the

combination of a group of metallic substationcircuits, apparatus at the substation of each metallic circuit consisting of a biased polarized call-bell and a condenser in a bridge between the line conductors, with telephones, a selecting-key, and a ringing-key, in parallel with the said bridge, the said keys being each adapted to ground a different one of the said line conductors and to open the other; and central-station apparatus comprising a polarized relay in each line conductor, the helices of said relays being connected to the opposite poles of a centrally-grounded source of-current,.a selecting and switching device operated through said line-relays, having a rotating switchingconnector in whose path are located terminals of its own main-line cond uctors and terminals of the main-line conductors of the other circuits with which it is multipled, with a source of pulsating ringing-current, and means for automatically switching the same to the ringing side of the metallic I circuit when the saidringing-key is manipulated; as set forth.

4. In an automatic telephone-exchange, the

combination-with a group of metallic substa- -tion-circuits; abiased polarized call-bell, anda condenser in series therewith bridged between the main conductors of each circuiti and telephones in a normally open branch of said bridge in parallel to said bell, all at each substation of said circuits; of a selecting-key and a ringing-key also in said branch at each substatiom'said keys being adapted each to ground a different one of said line conductors and to open the circuit of the other; a composition to which they have been moved in .a

local circuit jointly controlled by said relays; a pulsatory or intermittent call-current generator; and means for switching the same to the main conductor grounded by said ring ing-key'; the said battery, relays, switch mech anism, and call-generator being all at the central station; substantially as set forth.

5: In an automatic telephone-exchange, the combination of a group of metallic substation-circuits provided with a polarized relay in each line conduct-or having helices connected respectively to the poles of a centrallygrounded source of current, a selectingafnd switching device having fixed terminals for each main conductor normally connected-bya movable switching-connector with fitted multiple terminals associated with and in the path of the movable switching-connector of the other circuits respectively, a second (universal) fixed terminal for each metallic circuit adapted to be connected with one of the line conductors, and to be switched by the said movable connector to the terminal of any one of the associated circuits, a selectingelectromagnt responsive to the movement of the selecting-relay armature produced by in-.

terruptions of the main-line current and controlling the selecting mechanism of said. device, and a pawl-retaining electromagnet responsive through the medium of the said linerelays to a sustained main-line current all at the central station; and at each substation,

an automatic switch adapted to close the circuit continuously for the establishment of the said sustained current for the operation of the polarized relays, and a selecting-key for grounding one side of the main line and open ing the'other .to produce'current interruptions for the operation of said selecting-mag net; as set forth.

6, In an automatic telephone-exchange, the combination of a group of metallic substationcircuits provided with a polarized relay in each line conductor, said relays having their helices connected to the oppositepoles of a centrally-grounded battery; a selecting, andswitching device for each circuit comprising fixed terminals for each-main conductor normally connected by a movable switchingconnec'tor with fixed multiple terminals of said main conductors associated with and in the path of the movable switching-connector of the other circuits respectively, two universal fixed terminals foreach metallic circuit adapted to be connected with the line conductors and to be switched by the said movable connector; into connection with the terminals of. any, one-of the associated circuits, 9. selecting- I electromagnet responsive to the movement of 1 the selecting-relay armature, produced by interruptio'ns ofj the main-line current and con"- trolling the selecting mechanism of said de-' vice, and a pawl-retaining electromagnet responsive through the medium of the said line relays to a sustained main-line current-to actuate the said polarized relays, all atthe central station; and at each substation, anauto matic switch adapted to close the circuit continuously for the establishment of the said sustained current for the operation of the polarized relays; and a selecting-key for ground-' ing one side of the main line and opening the other to'produce cu rrent in-terru ptions for the operation of said selecting-magnet through the medium of said selecting-relay; as set forth. I v

7. A selecting and switching device, consisting of a base-plate upon which are niounted a' selecting-electromagn'et and a retaining-electromagnet, standards secured to said plate to which are pivoted the armatures of said mag- I nets which are provided with extensions upon one end thereof, respectively supporting a selecting-pawl and aretaining-pawl, a spindle I journaled in said standards having a recoveryspring and supporting on one end insulated switching-springs, and upon the opposite end a ratchet-wheel between'said extensions and in proximity to said pawls; with insulated line-conductor terminals supported on a dial formed'of one of said standards and in the path of said switching-springs; as set forth.

,8. The combination in an automatic telephone-exchange, of a group of metallic substation-circuits, a call-bell and'condenser in a bridge and an automatic switch, selecting-key and ringing-key in a parallel branch of said bridge at eachsubstation, the said switch be ing adapted to close the normally open linecircuit, and each key to open the circuit and ground a line conductor; with. selecting and switching apparatus at the central station, consisting of a polarized relay in each line conductor joined to a centrally-grounded battery, a switching device with a pair of switchingsprings, in the path of which are concen= trio pairs of terminals, representing respecthe multipled terminals at allof the switching devices of said group, each of saidsfprings normally resting upon and connecting the terminals of itsown line conductors with its own multiple terminals in all saiddevices, one of the latter or multiple ,terminals having a1 branch containing a con user to one of the line conductgbrs? :5 Sci ing eliectromagnet to rotate the switchingsprings, ahd a retaiiningelectromagnet to maintain the springs in positionfon the terminals; with a pulsatory or intermittent call-current generator in a normally incomplete circuit;. the said apparatus adapted, to become operative and to cause each line-relay to close independent local circuits and energize the retaining-magnet when the main circuit is closed by its substationsswitch,

' to deenergi'ze thelringing polarized relay,-and

provide a; pathw f or the ringing-current through the call-bell and switchingdevice ofa selected substation-circuit in response to the manipu; lation of .said ringing-key L substantially as described-.

' 9. In anautomatic telephone-exchange system, the combination with two or more metallic substation-circuits leading to a central vs 'on'; of selector mechanism at the central statl n .for connecting a calling with a called subs ion-line, said mechanism comprising terminals representingthe'substations, and a movable connector adapted to connect terminals of the calling and any called substationcircuit; ringing and selecting relays in the conductors of the calling-circuit respectively; electromagnetic actuating means for advancing the connector; a circuit through said electromagnet closed by the simultaneous energization of the ringing relay and the deem ing the circuit through the ringing-relay.

10. In an automatic telephone-exchange systively the line conductors of' said device and I V tem, the combination with two or more metallic substation-circuits leading to a central statlon; of selector mechanism at the central station for connecting a calling With-a called? controlof the calling-substation for simultaneously grounding 'a circuit by way of one I conductor of the calling substation circuit through the ringing-relay and opening the circh in through the selecting-relay; a ringing-circult closed by the simultaneous energization of the selecting relay and deenergization of the ringingrelay, said ringing-circuit extending, through the terminals connected by the connector-to the called line; means under con-- trolof the calling-substation for simultane ously groundinga circuit by Wayof one line through the selecting-relay and opening the circuit through the ringing-relay; return motor means in which power is stored up by the advance of the connector; electromagnetic re- 7 tain1ng.means for holding the connector 1n' its advanced position; and a circuit through 'Correction in Lelters Patent No. 772,024.

the electromagnet of the retaining means closed by the energization of both or eitherone of the relays to hold the retaining means in operative position, and opened by the sirnultaneous deenergizationof both relays to release the retaining means.

11. In an automatic telephone-exchange systennthe combination with two or more subwaoaa station-circuits leading to a central station; selectlng and switching mechanism it ll bile central station, one for each sfibstation-circuit,

each of said mechanisms I comprising a fixed terminal for each of the two ma1n line-con ductors of all of the substation-circuits includsubstation-circuit conductors and to thereby connect each of its own substation-circuit conductors to-its corresponding terminals at their other selecting and switching mechanisms, a second fixed terminal for each main-line conductor of its ownsubstation conductors, and

motor mechanism for moving the connector to connect its own substation-circuit conductors with the terminalsof the conductors of any other substation-circuit, or with said second terminals of its own substation-circuit when two subscribers both on said circuit wish to communicate with each other.

In testimony whereof I have signedmy name to this s pecification, in the presence of twosubscribing witnesses, this 21st day of January,-

- ALBERT M. BULLARD.

Witnesses:

HARRY B. THAYER, ALBERT L. SAER.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 22d day of January,

It is hereby certified that in Letters Patent No. 772,024,;granted October'll, 1904;, upon the application of Albert M. Ballard, of New York, N. Y., and Louis A. Falk,

of Boston, Massachusetts, for an improvement in f Automatic Telephone-Exchange System and Apparatus, an error appears in the printed specification requiring correction, as follows: In line 39, page 6, the word multiplied? should read multipled; and

that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st dav of November, A. 1)., 1904.

[SEAL.]

,F. I. ALLEN,

Commissioner of Patents.

V tem, the combination with two or more metallic substation-circuits leading to a central statlon; of selector mechanism at the central station for connecting a calling With-a called? controlof the calling-substation for simultaneously grounding 'a circuit by way of one I conductor of the calling substation circuit through the ringing-relay and opening the circh in through the selecting-relay; a ringing-circult closed by the simultaneous energization of the selecting relay and deenergization of the ringingrelay, said ringing-circuit extending, through the terminals connected by the connector-to the called line; means under con-- trolof the calling-substation for simultane ously groundinga circuit by Wayof one line through the selecting-relay and opening the circuit through the ringing-relay; return motor means in which power is stored up by the advance of the connector; electromagnetic re- 7 tain1ng.means for holding the connector 1n' its advanced position; and a circuit through 'Correction in Lelters Patent No. 772,024.

the electromagnet of the retaining means closed by the energization of both or eitherone of the relays to hold the retaining means in operative position, and opened by the sirnultaneous deenergizationof both relays to release the retaining means.

11. In an automatic telephone-exchange systennthe combination with two or more subwaoaa station-circuits leading to a central station; selectlng and switching mechanism it ll bile central station, one for each sfibstation-circuit,

each of said mechanisms I comprising a fixed terminal for each of the two ma1n line-con ductors of all of the substation-circuits includsubstation-circuit conductors and to thereby connect each of its own substation-circuit conductors to-its corresponding terminals at their other selecting and switching mechanisms, a second fixed terminal for each main-line conductor of its ownsubstation conductors, and

motor mechanism for moving the connector to connect its own substation-circuit conductors with the terminalsof the conductors of any other substation-circuit, or with said second terminals of its own substation-circuit when two subscribers both on said circuit wish to communicate with each other.

In testimony whereof I have signedmy name to this s pecification, in the presence of twosubscribing witnesses, this 21st day of January,-

- ALBERT M. BULLARD.

Witnesses:

HARRY B. THAYER, ALBERT L. SAER.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 22d day of January,

It is hereby certified that in Letters Patent No. 772,024,;granted October'll, 1904;, upon the application of Albert M. Ballard, of New York, N. Y., and Louis A. Falk,

of Boston, Massachusetts, for an improvement in f Automatic Telephone-Exchange System and Apparatus, an error appears in the printed specification requiring correction, as follows: In line 39, page 6, the word multiplied? should read multipled; and

that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st dav of November, A. 1)., 1904.

[SEAL.]

,F. I. ALLEN,

Commissioner of Patents.

It is hereby certified that in Letters Patent No. 772,024, granted Octoberll, 1904, upon the a iplication of Albert M. Ballard, of New York, N. Y., and Louis A. Falk, of Boston, Massachusetts, for an improvement in Automatic Telephone-Exchange System and Apparatus, an error appears in the printed specification requiring eon-eetion, as follows: In line 39, page 6, the word multiplied? should read multipled; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st dav of November, A. D. 1904.

' F. I. ALLEN,

[SEAL Commissioner of Pdtents. 

